neural tube

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A dorsal tubular structure in the vertebrate embryo that is formed by longitudinal folding of the neural plate and that differentiates into the brain and spinal cord.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun anatomy hollow longitudinal dorsal tube formed in the folding and subsequent fusion of the opposite ectodermal folds in the embryo that gives rise to the brain and spinal cord

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a tube of ectodermal tissue in the embryo from which the brain and spinal cord develop